Extrinsic point defects, i.e., oxygen vacancies, might lead to exciting improvements in advanced ceramic materials' functional properties. For instance, oxygen vacancies decreased band gap width in advanced ceramic materials, and more specifically, in lead-free piezoceramic BaTiO3, increased relative permittivity, and improved its densification. In this work, BaTiO3 (pure and Zr-doped) was quickly densified by rapid pressure-less sintering to obtain dense ceramics with fine microstructure. Optimal sintering conditions of heating rate 100 °C/min to 1230 °C sintering temperature with a 5 min dwell were applied. Oxygen vacancies were later induced by annealing in various reducing atmospheres at the temperature of 900 °C. The presence of oxygen vacancies in the lattice and the reducing effect of the annealing was indicated in several ways: colour change of the samples, Raman spectroscopy showed a red-shifted signal caused by changes in the crystalline structure (Figure 1.), X-ray diffraction analysis confirmed the change of the lattice parameters, X-ray photoelectron spectroscopy showed the change of the chemical bonds and valence states, and electron paramagnetic resonance directly measured the amount of oxygen vacancies. The influence of oxygen vacancies on the functional properties of BaTiO3-based ceramics was described in terms of dielectric and piezoelectric properties.